Metformin Enhances Plant Immunity by Blocking BIK1-Mediated CPK28 Phosphorylation

Academic Background

In the context of the increasingly severe global food security issues, controlling crop diseases has become a major challenge in agricultural production. Although traditional chemical pesticides can effectively control diseases, the environmental pollution and health problems caused by their excessive use cannot be ignored. Therefore, developing chemical inducers that can activate the plant’s own immune system has become a sustainable strategy for disease control. Metformin (Met), a widely used drug for the treatment of type 2 diabetes, has been extensively studied for its functions in mammalian cells, but its mechanism of action in plants remains unclear. This study aims to explore the role of metformin in inducing plant immunity and its related mechanisms, providing a scientific basis for the development of novel plant immunity inducers.

Research Source

The research team consists of experts and scholars from several renowned universities and research institutions, including Daolong Dou from Nanjing Agricultural University and Xiangxiu Liang from South China Agricultural University. The study was accepted on February 22, 2024, and published online in the Journal of Advanced Research (Volume 68, 2025) on March 3, 2024.

Research Process and Results

Research Process

1. Metformin’s Induction of Plant Immunity
   Researchers first treated Arabidopsis thaliana leaves by spraying different concentrations of metformin and measured the expression levels of defense genes (such as FRK1, GST1, PR1, and NHL10). The results showed that metformin significantly upregulated the expression of defense genes, and this induction was dose-dependent.
   Subsequently, researchers verified the enhancement of plant immune responses by metformin through experiments on ROS (Reactive Oxygen Species) accumulation and MAPK (Mitogen-Activated Protein Kinase) phosphorylation. The results indicated that metformin significantly induced ROS accumulation and MAPK phosphorylation, suggesting its ability to activate the plant immune system.

2. Pathogen Infection Experiments
   To further evaluate the efficacy of metformin in controlling plant diseases, researchers sprayed Arabidopsis thaliana leaves with different concentrations of metformin and then inoculated them with the pathogen Pseudomonas syringae pv. tomato (Pst) DC3000. The results showed that metformin significantly enhanced plant resistance to the pathogen. Additionally, metformin also increased resistance to pathogens like Phytophthora capsici in crops such as tomato, soybean, and pepper.

3. Mechanism of Metformin’s Action
   Using surface plasmon resonance (SPR) and microscale thermophoresis (MST) techniques, researchers identified calcium-dependent protein kinase 28 (CPK28) as a potential target of metformin. Further experiments revealed that metformin blocked the interaction between BIK1 and CPK28, inhibiting BIK1-mediated CPK28 phosphorylation, thereby alleviating CPK28’s negative regulation of immune responses.
   Molecular docking experiments predicted that metformin forms hydrogen bonds with T76 and D209 in the kinase domain of CPK28, thus inhibiting CPK28’s function. Mutation experiments confirmed that the T76 site is a key binding site for metformin to CPK28 and is essential for its function.

Main Results

1. Metformin significantly enhances plant resistance to pathogens and induces plant immune responses by activating MAPK, upregulating defense gene expression, and enhancing ROS bursts.
   
2. CPK28 is the direct target of metformin. By blocking the interaction between BIK1 and CPK28, metformin inhibits BIK1-mediated CPK28 phosphorylation, thereby alleviating CPK28’s negative regulation of immune responses.
   
3. Metformin exhibits broad-spectrum anti-pathogen activity in crops such as tomato, soybean, and pepper, demonstrating its potential application value.

Research Conclusion

This study discovered that metformin and its derivatives constitute a novel class of broad-spectrum plant immunity inducers. Metformin enhances plant immune responses by targeting CPK28 and inhibiting BIK1-mediated CPK28 phosphorylation. This mechanism provides a theoretical basis for the development of novel plant immunity inducers. Additionally, this study demonstrates the potential of plant systems as models for studying the functions and mechanisms of metformin, offering new insights into exploring metformin’s other roles in mammals.

Research Highlights

1. Novel Plant Immunity Inducer: This study is the first to discover that metformin and its derivatives can serve as broad-spectrum plant immunity inducers, providing a new chemical tool for sustainable plant disease control.
   
2. Mechanism Elucidation: For the first time, researchers elucidated the molecular mechanism by which metformin enhances plant immunity by blocking the interaction between BIK1 and CPK28, providing a new perspective for understanding plant immune regulation.
   
3. Potential Application Value: Metformin exhibits significant anti-pathogen activity in various crops, showcasing its potential application value in agricultural production.

Significance and Value

This study not only provides a scientific basis for the development of novel plant immunity inducers but also offers new insights into exploring other roles and mechanisms of metformin in mammals. By activating the plant’s own immune system to control diseases, the use of chemical pesticides can be reduced, thereby lowering environmental pollution and health risks. Additionally, this study demonstrates the potential of plant systems as models for studying the functions and mechanisms of metformin, providing new directions for future related research.